From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 382B6C2BA17 for ; Mon, 6 Apr 2020 16:07:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED7A024924 for ; Mon, 6 Apr 2020 16:07:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729404AbgDFQHI (ORCPT ); Mon, 6 Apr 2020 12:07:08 -0400 Received: from fieldses.org ([173.255.197.46]:51964 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729180AbgDFQHH (ORCPT ); Mon, 6 Apr 2020 12:07:07 -0400 Received: by fieldses.org (Postfix, from userid 2815) id E97F01513; Mon, 6 Apr 2020 12:07:06 -0400 (EDT) Date: Mon, 6 Apr 2020 12:07:06 -0400 From: "J. Bruce Fields" To: Miklos Szeredi Cc: Lennart Poettering , Ian Kent , David Howells , Christian Brauner , Linus Torvalds , Al Viro , dray@redhat.com, Karel Zak , Miklos Szeredi , Steven Whitehouse , Jeff Layton , andres@anarazel.de, keyrings@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Aleksa Sarai Subject: Re: Upcoming: Notifications, FS notifications and fsinfo() Message-ID: <20200406160706.GC2147@fieldses.org> References: <2590640.1585757211@warthog.procyon.org.uk> <36e45eae8ad78f7b8889d9d03b8846e78d735d28.camel@themaw.net> <27994c53034c8f769ea063a54169317c3ee62c04.camel@themaw.net> <20200403111144.GB34663@gardel-login> <20200403151223.GB34800@gardel-login> <20200403203024.GB27105@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The patch makes sense to me, thanks! In the NFS case it's implementing the "mountpoint" export option: mountpoint=path mp This option makes it possible to only export a directory if it has successfully been mounted. If no path is given (e.g. mountpoint or mp) then the export point must also be a mount point. If it isn't then the export point is not exported. This allows you to be sure that the directory underneath a mountpoint will never be exported by accident if, for example, the filesys‐ tem failed to mount due to a disc error. If a path is given (e.g. mountpoint=/path or mp=/path) then the nominated path must be a mountpoint for the exportpoint to be exported. --b. On Mon, Apr 06, 2020 at 10:35:55AM +0200, Miklos Szeredi wrote: > From: Miklos Szeredi > Subject: statx: add mount_root > > Determining whether a path or file descriptor refers to a mountpoint (or > more precisely a mount root) is not trivial using current tools. > > Add a flag to statx that indicates whether the path or fd refers to the > root of a mount or not. > > Reported-by: Lennart Poettering > Reported-by: J. Bruce Fields > Signed-off-by: Miklos Szeredi > --- > fs/stat.c | 3 +++ > include/uapi/linux/stat.h | 1 + > 2 files changed, 4 insertions(+) > > --- a/include/uapi/linux/stat.h > +++ b/include/uapi/linux/stat.h > @@ -172,6 +172,7 @@ struct statx { > #define STATX_ATTR_NODUMP 0x00000040 /* [I] File is not to be dumped */ > #define STATX_ATTR_ENCRYPTED 0x00000800 /* [I] File requires key to decrypt in fs */ > #define STATX_ATTR_AUTOMOUNT 0x00001000 /* Dir: Automount trigger */ > +#define STATX_ATTR_MOUNT_ROOT 0x00002000 /* Root of a mount */ > #define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */ > > > --- a/fs/stat.c > +++ b/fs/stat.c > @@ -202,6 +202,9 @@ int vfs_statx(int dfd, const char __user > error = vfs_getattr(&path, stat, request_mask, flags); > stat->mnt_id = real_mount(path.mnt)->mnt_id; > stat->result_mask |= STATX_MNT_ID; > + if (path.mnt->mnt_root == path.dentry) > + stat->attributes |= STATX_ATTR_MOUNT_ROOT; > + stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT; > path_put(&path); > if (retry_estale(error, lookup_flags)) { > lookup_flags |= LOOKUP_REVAL;